Add support for multiple conditions to initctl cond set/clr

[troglobit]

As mentioned in #326, it would be great to act on all conditions given on the command line to initctl cond set/clr.

initctl cond set a/b/c d/e/f

Originally posted by @hongkongkiwi in https://github.com/troglobit/finit/issues/326#issuecomment-1342491904